Printers for printing out the outputs of computers are understandably varied in configuration. Two very popular groups, exemplified by NEC Models 2000/3500/8000 and Diablo HyType II, are of the daisy wheel type, printing a whole character with each stroke of printer operation. These printers employ a ribbon cartridge wherein a ribbon wound on and between two spools is impacted by a character print element of the printer. Cartridge configurations for these printers are illustrated by U.S. Pat. Nos. 4,496,255, to Meintrup et al, 4,533,266 and to Shapiro; and 4,544,291 to Kano. A principal characteristic of such cartridges is that they employ two laterally spaced capstan drives, alternately driven through opposite sides of the cartridge by a rotary drive member of a host printer. One of the capstan drives rotates a ribbon in one direction, wherein a top region of the ribbon is utilized in printing, and the other capstan drive rotates the ribbon in the opposite direction and a bottom region of the ribbon is utilized. Each of the capstan drives consists of a drive roller and a pinch roller, and each capstan drive is associated with one of two spools of the cartridge. A belt is coupled between the driven roller and its associated spool, driving this spool, as a take-up spool, in a direction to receive the ribbon. This belt is positioned on the outside of the cartridge, connecting between pulleys on shafts of the drive roller and spool. In order to switch directions of drive, the cartridge is turned over and the belt is removed from pulleys on one side of the cartridge and placed around pulleys on the opposite side.
A still further disadvantage is that the cartridges are for use in only a single type of printer because the position and direction of rotation of the output drive shaft of the printer is fixed as is the position of the holding mechanism for securing the cartridge in the printer. Thus, to be capable of being used in other types of printers, the cartridge must be capable of receiving printer drive shafts which may rotate in a different direction and from varying locations, while being held in the printer by different types of holding devices. None of these references provide such a capability.
The belt and pulley arrangement discussed is an obvious disadvantage, both from the point of view of inconvenience and the variable tension effected upon the take-up spool as the amount of ribbon on it changes. Perhaps in recognition of the most blatant of these, the inconvenience, Meintrup suggests that an internal belt might be employed and cites a data tape cartridge manufactured by the 3M Company as providing such. This cartridge or cassette is illustrated in Von Behren U.S. Pat. No. 3,692,255, and a ribbon cartridge counterpart of it is illustrated in Sasaki U.S. Pat. No. 4,528,572. Upon examination of these references, it appears that both employ a single, centrally positioned drive member and thus are employable only with drive units, tape drives or printer drives, adapted to interface with a central position on a cartridge and not one where separate, spaced capstan drives are employed as required by the printers referred to above. Clearly, neither of these patents provide a teaching as to how one would employ an internal belt in a ribbon cartridge where the drive positions are spaced apart as in the class of cartridge we are concerned with here. In contrast, the inapplicability is manifest and is obvious from the fact that if a belt were stretched between the capstan drives of Meintrup, with an idler symmetrically positioned, e.g., where the drive roller is positioned in the case of Sasaki, the ribbon would be driven by the belt in one direction and the ribbon spool in an opposite direction, an inoperative condition.
The patent to Daughters, U.S. Pat. No. 4,307,969, provides a cartridge for use in two different printing machines having drive locations of varying spatial locations as well as direction of rotation. While the Daughters patent is entitled "Universal Ribbon Cartridge," it is only universal to the extent that it can be used in two printers. The first printer must have its drive shaft located to the left and rotatable in a counterclockwise direction, while the drive shaft of the second printer must be placed in a position which is generally adjacent to and slightly inwardly of the drive shaft of the first printer, and the drive shaft must rotate in a counterclockwise direction. No provision is made in the patent to Daughters for driving the tape from different drive shaft locations and rotations from the other (right side) of the cartridge. Additionally, the patent to Daughters is driven by an external belt and, therefore, has the same disadvantage as discussed above in conjunction with the variable tension effected upon the take-up spool as the amount of ribbon on it changes. Further, the cartridge to Daughters permits only one pass of the ribbon through the impact region of the printer. It does not provide for the cartridge to be turned over so that the unused portion (upper or bottom half) of the ribbon may be used in a second pass of the ribbon through the printer.
A still further matter of concern with respect to the merit of ribbon cartridges is that of rate of use of ribbon. Ideally, the ink in the vicinity of an impact by a printing element will be completely utilized but not to the extent that a portion of a character being printed will receive insufficient ink. Pertinently, the rate of ribbon usage is a function of the speed of the rotating drive of the printer and the translation of this speed to a final ribbon drive speed, the latter being a function of the drive mechanism of the cartridge. Since the drive speed is thus fixed by a printer manufacturer, it is up to the ribbon cartridge manufacturer to provide a cartridge which will provide an optimum rate of ribbon advancement for the drive speed at hand. Unfortunately, it appears that because of certain structural limitations imposed by the mechanisms employed in prior art ribbon cartridges, they effect a higher rate of ribbon travel than is actually necessary to provide good print quality. Specifically, it appears that this is the result of employing a direct capstan drive of ribbon, which in turn has necessitated the employment of toothed surfaces to obtain sufficient grip on a ribbon to reliably advance it. This in turn has resulted in an excessive effective diameter of the drive roller, resulting in an excessive effective rate of ribbon advancement. SUMMARY OF THE INVENTION
In accordance with this invention, alternately, any one of two drive wheels of a set of two spaced sets of drive wheels, driven by a printer, drives a belt internally located in a ribbon cartridge, and this belt engages the ribbon at two locations where it is wound on the spools, it further engages an idler roller, and it engages the other (then undriven) drive wheel of the other set. The ribbon is not engaged by a drive wheel either directly or through the thickness of the belt. The idler roller is positioned to hold the belt against the ribbon where it is wound on ribbon spools. The wheel which is driven by the drive shaft of the printer moves the belt (either directly or through its adjacent mating wheel of the set) across a wheel of the second set of drive wheels, then over the ribbon on one spool, around the idler roller, over the ribbon on the other spool, and back over the wheel of the driving set of rollers. The ribbon path takes it from one spool, through an impact region and onto the second spool. Optimum ribbon tension is maintained on the ribbon throughout its movement. A predetermined drive wheel of the two drive wheels of each set of wheels may be driven by the drive shaft of the printer. Additionally, the sets of drive wheels are positioned in a manner which permits the cartridge to be turned over so that a wheel of the other set engages the drive shaft of the printer so that the ribbon may pass through the impact region of the printer for a second time to permit the unused portion (upper or lower half of the ribbon) to be used.